When it comes to cancer risk in animals, the rule of thumb is the older and bigger you are, the more likely your species is to get cancer. However, there are some notable exceptions to this rule in the animal kingdom—for example, whales. A new study published this week in Molecular Biology and Evolution set out to uncover why, according to a press release from Arizona State University.
The study, which was conducted by a team of scientists at Arizona State University, the University of Groningen in the Netherlands, the Center for Coastal Studies in Massachusetts and nine other cancer research institutions around the world examined the genome of the humpback whale and nine other cetaceans (the mammalian family that includes whales, dolphins and porpoises) to study potential cancer suppression mechanisms in their DNA.
Why whales? Often, with large-bodied animals, the number of cell divisions required to maintain a healthy body puts an organism at an increased risk for cancer. Whales also live much longer than most mammals and have a much higher percentage of body fat—factors also linked to cancer. However, whales have a far lower risk for the disease than most other animals, a fact that has confounded scientists.
To determine why this is the case, the team obtained skin samples from various whales, mapped out their DNA sequences and compared them to look for parts of the genome that had evolved to help whales adapt to life in the ocean. They found that some parts of the whale genome—many of which are related to genes that regulate cell cycle, cell proliferation and DNA repair, processes that are key for normal cell function—appear to have evolved faster than in other mammals. The whale genome also evolved many duplications of tumor-suppressing genes key to fighting cancer.
“Nature is showing us that these changes to cancer genes are compatible with life. The next questions are, which of these changes are preventing cancer, and can we translate those discoveries into preventing cancer in humans?” said Carlo Maley, PhD, a cancer evolutionary biologist at Arizona State University’s Biodesign Institute and one of the study’s senior authors.
Moving forward, the team will do further research to better understand whales’ cancer-suppressing mechanisms using experiments with whale cell lines, which over time may lead to the development of whale-derived human cancer drugs.